JP2008090203A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of efficiently discharging heat produced by a light source and sufficiently preventing dust or the like, from being stuck to a light diffusion plate so as to prevent screen irregularities. <P>SOLUTION: The liquid crystal display device is constituted by arranging a plurality of light sources 3 on the rear side of the light diffusion plate 2, arranging a lamp box 4 on the rear side of the plurality of light sources 3, and arranging a liquid crystal panel 12 having a liquid crystal cell 6 on the front side of the light diffusion plate 2. The diagonal length of an image display section of the liquid crystal panel 12 is ≥60 cm, a ventilation passage 10 connected to the outside for discharging heat from the light sources 3 to outside the device 1 is provided in contact with at least one surface of the light diffusion plate 2, and the surface resistivity of the surface of the light diffusion plate 2 which comes into contact with the ventilation passage 10 is set to ≤1.0×10<SP>14</SP>Ω/sq. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device suitable as, for example, a large liquid crystal television.

  In this specification and claims, the term “surface resistivity” means a surface resistivity measured in accordance with JIS K6911.

  As a liquid crystal display device, a configuration in which a surface light source device is disposed as a backlight on the back side of a liquid crystal panel is known. As the surface light source device, a surface light source device having a configuration in which a plurality of light sources are disposed in a lamp box having an inner surface provided with a light reflecting layer and a light diffusion plate is disposed on the front side of these light sources is known. Yes.

By the way, in recent years, the enlargement of liquid crystal display devices, especially liquid crystal televisions, has been progressing rapidly, but in order to ensure a sufficient luminance by enlarging the screen, the number of light sources must be increased. In addition, since the amount of heat generated by the backlight is greatly increased, it is necessary to provide a discharge mechanism for efficiently discharging the heat generated by the backlight when the size is increased. For example, there is known one that can discharge heat inside the backlight to the outside by blowing air with a heat exhaust fan. In addition, a chimney structure that forms air vents on the lower and upper surfaces of the rear part of the cabinet of the liquid crystal display device and generates natural convection is used. Also known is a system in which the heat generated inside the backlight is discharged and cooled by exhausting the air outside and sucking cold air from the ventilation holes on the lower surface (see Patent Document 1).
JP 2005-84354 A

  However, in the liquid crystal display devices described in Patent Documents 1 and 2 described above, light is diffused by cooling the air by replacing the air inside the backlight by blowing with a heat exhaust fan or by natural convection. There has been a problem that dust or the like tends to adhere to the surface of the plate. When dust or the like adheres to the surface of the light diffusing plate, the brightness of the attached portion decreases, and this portion becomes conspicuous as screen unevenness.

  The present invention has been made in view of such a technical background, and is capable of efficiently discharging the heat generated by the light source and sufficiently preventing dust and the like from adhering to the light diffusion plate. An object of the present invention is to provide a liquid crystal display device capable of preventing the above-described problem.

  In order to achieve the above object, the present invention provides the following means.

[1] A plurality of light sources are arranged on the back side of the light diffusing plate, a lamp box is arranged on the back side of the plurality of light sources, and a liquid crystal panel including a liquid crystal cell is arranged on the front side of the light diffusing plate. A liquid crystal display device comprising:
The diagonal length of the image display part in the liquid crystal panel is 60 cm or more,
A surface of the light diffusing plate that is in contact with the air flow channel is provided with a vent channel that communicates with the outside for discharging heat generated from the light source to the outside of the apparatus. The surface resistivity of the liquid crystal display device is 1.0 × 10 ¹⁴ Ω / □ or less.

[2] The preceding item, wherein the ventilation channel is provided in contact with the light source side surface of the light diffusion plate, and the surface resistivity of the light diffusion side surface of the light diffusion plate is 1.0 × 10 ¹⁴ Ω / □ or less. 2. A liquid crystal display device according to 1.

[3] The liquid crystal display according to item 1, wherein the air flow path is provided in contact with both surfaces of the light diffusion plate, and the surface resistivity of both surfaces of the light diffusion plate is 1.0 × 10 ¹⁴ Ω / □ or less. apparatus.

  [4] The liquid crystal display device according to any one of items 1 to 3, wherein the light diffusing plate is formed of a resin plate in which an antistatic agent is dispersed in a transparent resin.

  [5] In the light diffusion plate, a surface layer in which an antistatic agent is dispersed in a transparent resin is laminated on a surface of the base layer in which the light diffusing agent is dispersed in a transparent resin, on the side in contact with the ventilation channel. 4. The liquid crystal display device according to any one of items 1 to 3, comprising a laminated plate.

In the liquid crystal display device according to the invention of [1], since the ventilation channel communicating with the outside for discharging heat generated from the light source to the outside of the device is provided, the diagonal length of the image display unit is 60 cm or more. Despite the large size, the heat generated by the light source can be discharged and cooled. Further, the surface of the light diffusing plate that is in contact with the air flow path has a surface resistivity of 1.0 × 10 ¹⁴ Ω / □ or less and excellent antistatic properties, so that dust or the like enters the air flow path. However, it is possible to prevent the dust and the like from adhering to the surface of the light diffusion plate, thereby preventing the occurrence of screen unevenness.

  In the invention [2], since the ventilation channel is provided in contact with the light source side surface of the light diffusion plate, heat generated from the light source can be more efficiently removed.

  In the invention of [3], since the ventilation channel is provided in contact with not only the light source side surface of the light diffusion plate but also the non-light source side surface, heat generated from the light source can be removed more efficiently. it can.

  In the invention of [4], the light diffusing plate is composed of a resin plate in which an antistatic agent is dispersed in a transparent resin, and thus has excellent durability for antistatic performance.

  In the invention of [5], since the antistatic agent is dispersed in the transparent resin, the durability of the antistatic performance is excellent. Furthermore, since the light diffusing agent is dispersed in the base layer and the antistatic agent is dispersed in the surface layer, and thus the light diffusing agent and the antistatic agent are not coexisting, the surface state of the light diffusing plate is good and glossy. Unevenness can also be prevented.

  One embodiment of a liquid crystal display device (1) according to the present invention is shown in FIG. In FIG. 1, (11) is a surface light source device, and (12) is a liquid crystal panel.

  The liquid crystal panel (12) includes a liquid crystal cell (6) and polarizing plates (7) and (8) disposed on both upper and lower sides of the liquid crystal cell (6). The diagonal length of the rectangular image display unit in the liquid crystal panel (12) (the diagonal length of the rectangular image display surface visible to the user from the front side) is 60 cm or more. The diagonal length of the image display unit is usually set in the range of 60 to 200 cm.

  The said surface light source device (11) is arrange | positioned at the lower surface side (back side) of the said lower polarizing plate (8). The surface light source device (11) has a thin box-shaped lamp box (4) having a rectangular shape in plan view and an open upper surface side (front surface side), and a lamp box (4) spaced apart from each other. A plurality of light sources (3), a light diffusing plate (2) disposed on the upper side (front side) of the plurality of light sources (3), and an upper side (front side) of the light diffusing plate (2) And an optical film (5) having a light collecting function (lens function). A light reflecting layer (not shown) is provided on the inner surface of the lamp box (4).

  In addition, a ventilation channel (10) is provided in contact with the light source (3) side surface of the light diffusion plate (2). That is, a ventilation channel (10) communicating with the outside for releasing heat from the light source (3) to the outside of the device (1) is provided between the light diffusion plate (2) and the lamp box (4). Is provided. By providing ventilation gaps (31) (31) between both ends of the light diffusion plate (2) and both ends of the lamp box (4), the ventilation channel (10) communicates with the outside. ing. The liquid crystal display device (1) may be provided with a blower fan for sending air into the ventilation channel (10).

In this embodiment, the light diffusing plate (2) is transparent on the surface (lower surface) on the side in contact with the ventilation channel (10) in the base layer (21) obtained by dispersing a light diffusing agent in a transparent resin. It consists of a laminated plate in which a surface layer (22) obtained by dispersing an antistatic agent in a resin is laminated, and the surface resistivity of the surface of the light diffusing plate (2) on the light source (3) side (that is, the surface resistance of the lower surface of the surface layer). Ratio) is set to 1.0 × 10 ¹⁴ Ω / □ or less.

  In the liquid crystal display device (1) according to the above configuration, the ventilation channel (10) communicating with the outside for discharging the heat generated from the light source (3) to the outside of the device (1) is provided. Even though the diagonal length of the portion is a large size of 60 cm or more, the heat generated by the light source can be efficiently discharged and cooled.

Further, the surface of the light diffusion plate (2) that is in contact with the ventilation channel (10) has a surface resistivity of 1.0 × 10 ¹⁴ Ω / □ or less and excellent antistatic properties. 10) Even if foreign matter such as dust enters the surface, it is possible to prevent the foreign matter such as dust from adhering to the surface of the light diffusion plate (2), thereby preventing the occurrence of screen unevenness. .

  Further, since the antistatic agent is dispersed and contained in the transparent resin to impart the antistatic property to the light diffusion plate (2), the antistatic performance is excellent in durability.

FIG. 2 shows another embodiment of the liquid crystal display device (1) of the present invention. The optical film (5) and the light diffusing plate (2) are spaced apart to form a ventilation channel (10X) between these (5) and (2), and in the light diffusing plate (2) Except for the fact that a surface layer (22) in which an antistatic agent is dispersed in a transparent resin is also laminated on the surface (upper surface) on the side in contact with the ventilation channel (10X), FIG. Since the configuration is the same as that of the liquid crystal display device shown in FIG. 1, the same components are denoted by the same reference numerals and the description thereof is omitted. In addition, the surface resistivity of the surface (upper surface) in contact with the ventilation channel (10X) in the light diffusion plate (2) is set to 1.0 × 10 ¹⁴ Ω / □ or less.

In the liquid crystal display device shown in FIG. 2, the ventilation channel (10) is not only provided in contact with the light source (3) side surface (lower surface) of the light diffusion plate (2), but also the non-light source side surface ( Since the ventilation channel (10X) is also provided in contact with the upper surface), the heat generated from the light source (3) can be more efficiently removed. Also, the upper and lower surfaces of the light diffusion plate (2) that are in contact with the ventilation channel (10) (10X) have a surface resistivity of 1.0 × 10 ¹⁴ Ω / □ or less and are excellent in antistatic properties. Even if foreign matter such as dust enters the path (10) (10X), it is possible to prevent the foreign matter such as dust from adhering to the surface of the light diffusion plate (2). Can be prevented.

FIG. 3 shows still another embodiment of the liquid crystal display device (1) of the present invention. The optical film (5) and the light diffusing plate (2) are spaced apart to form a ventilation channel (10X) between these (5) and (2), and the light diffusing plate (2). The surface layer (22) in which the antistatic agent is dispersed in the transparent resin on the surface (upper surface) of the base layer (21) in which the light diffusing agent is dispersed in the transparent resin, on the side in contact with the ventilation channel (10X). ) Is used, and the end of the light diffusing plate (2) and the end of the lamp box (4) are joined to make the inner space of the lamp box (4) a closed space. Since the configuration is the same as the configuration of the liquid crystal display device shown in FIG. 1 except that the configuration is adopted, the same components are denoted by the same reference numerals and the description thereof is omitted. In addition, the surface resistivity of the surface (upper surface) in contact with the ventilation channel (10X) in the light diffusion plate (2) is set to 1.0 × 10 ¹⁴ Ω / □ or less.

In the liquid crystal display device shown in FIG. 3, since the ventilation channel (10X) is provided in contact with the non-light source side surface (upper surface) of the light diffusion plate (2), heat generated from the light source (3) is removed. be able to. Further, the surface of the light diffusion plate (2) that is in contact with the ventilation channel (10X) has a surface resistivity of 1.0 × 10 ¹⁴ Ω / cm ² or less and excellent antistatic properties. ) Can be prevented from adhering to the surface of the light diffusing plate (2), thereby preventing unevenness of the screen.

In the present invention, the surface resistivity of the surface in contact with the ventilation channel (10) (10X) in the light diffusing plate (2) is set to 1.0 × 10 ¹⁴ Ω / □ or less. The surface resistivity can be realized, for example, by dispersing an antistatic agent in the light diffusion plate (2). Especially, it is preferable that the surface resistivity of the surface which contacts the said ventilation | gas_flow path (10) (10X) in the said light diffusing plate (2) is set to 1.0 * 10 < ¹² > (omega | ohm) / square or less.

  The antistatic agent is not particularly limited, and examples thereof include alkyl sulfonic acids, alkyl benzene sulfonic acids, and olefinic sulfates such as Li, Na, Ca, Mg, and Zn salts thereof or metal salts thereof, Anionic surfactants such as phosphate esters of alcohols; Cationic surfactants such as tertiary amines, quaternary ammonium salts, cationic acrylic ester derivatives, cationic vinyl ether derivatives; amphoteric salts of alkylamine betaines And amphoteric surfactants such as amphoteric salts of carboxylic acid or alanine sulfonate; nonionic surfactants such as fatty acid polyhydric alcohol esters and polyoxyethylene adducts of alkyl (amine).

  As the light diffusing plate (2), any material can be used as long as it has a light diffusing function, but a substrate in which a light diffusing agent is dispersed in a transparent resin is preferably used. Among them, a surface layer (in which an antistatic agent is dispersed in a transparent resin, on the surface of the base layer (21) in which the light diffusing agent is dispersed in the transparent resin, on the side in contact with the ventilation channel (10) (10X)). A laminate obtained by laminating 22) is particularly preferably used. Such a laminate can be produced, for example, by a coextrusion method. In addition, it is preferable to disperse | distribute 0.1-2 mass parts of antistatic agents with respect to 100 mass parts of transparent resin which comprises the said surface layer (22).

  Although it does not specifically limit as transparent resin which comprises the said light diffusing plate (2), For example, a styrene resin, an acrylonitrile styrene resin, a methyl methacrylate resin, a methyl methacrylate styrene resin Polyethylene terephthalate resin, polycarbonate resin, elastomers such as styrene / butadiene block polymer and acrylic elastomer, polyolefin resins such as polypropylene, and the like. Of course, these blends may be used. Among these, it is preferable to use a styrene resin, a methyl methacrylate resin, or a polycarbonate resin in that the resin itself is less colored. Particularly preferred is a styrene resin or a methyl methacrylate resin, and in this case, better light diffusibility can be imparted.

  As a specific example of the light diffusing plate (2), for example, on the surface of the base layer (21) in which a light diffusing agent is dispersed in a styrene resin, on the side in contact with the ventilation channel (10) (10X), Examples thereof include a laminated plate in which a surface layer (22) obtained by dispersing an antistatic agent in a styrene-methyl methacrylate copolymer resin is laminated.

  The light diffusing agent constituting the light diffusing plate (2) is not particularly limited, and examples thereof include inorganic or organic transparent fine particles having a refractive index different from that of the transparent resin of the base material. For example, inorganic particles such as calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide, crosslinked or high molecular weight styrene resin particles, crosslinked or high molecular weight acrylic And resin particles that do not dissolve even during melt extrusion of resin particles and crosslinked siloxane resin particles.

  The “crosslinked resin particle” refers to a particle having a gel fraction of 10% or more when dissolved in acetone, and the “high molecular weight resin particle” refers to a weight average molecular weight (Mw). Indicates 500,000 to 5,000,000 resin particles.

  The light source (3) is not particularly limited, and examples thereof include a fluorescent tube, a halogen lamp, a tungsten lamp, and a light emitting diode.

  The liquid crystal display device (1) according to the present invention is not particularly limited to that of the above-described embodiment, and any design change is allowed as long as it does not depart from the spirit of the present invention as long as it is within the scope of the claims. Is.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Materials used>
Resin particle Y (light diffusing agent): cross-linked siloxane-based resin particle (Toray Fill DY33-719, manufactured by Toray Dow Corning Silicone Co., Ltd., refractive index 1.42, weight average particle diameter 2 μm)
<Example 1>
99.5 parts by mass of a styrene resin (refractive index 1.59), 0.2 parts by mass of the resin particles Y, 0.07 parts by mass of a benzotriazole-based ultraviolet absorber (“SUMISOB 200” manufactured by Sumitomo Chemical Co., Ltd.), After 0.13 parts by weight of a light stabilizer (“Tinubin 770” manufactured by Ciba Specialty Chemicals Co., Ltd.) was mixed with a Henschel mixer, it was melt-kneaded with a first extruder and supplied to a feed block.

  On the other hand, 100 parts by mass of a styrene-methyl methacrylate copolymer resin, 0.2 parts by mass of sodium stearylsulfonate as an antistatic agent, and a benzotriazole-based ultraviolet absorber (“Sumisorb 200” manufactured by Sumitomo Chemical Co., Ltd.) 0.5 After mixing 0.2 parts by mass of a hindered phenolic antioxidant (thermal stabilizer) (“IRGANOX1010” manufactured by Ciba Specialty Chemicals Co., Ltd.) with a Henschel mixer, melt kneading with a second extruder Then, it was supplied to the feed block.

The resin supplied from the first extruder to the feed block becomes an intermediate layer (base layer) (21), and the resin supplied from the second extruder to the feed block becomes a surface layer (both sides) (22) (22). Thus, a light diffusion plate (2) composed of a three-layer laminate having a width of 23 cm and a thickness of 3 cm (intermediate layer 2.85 mm, surface layer 0.075 mm × 2) was produced. The surface resistivity of both surfaces of this light diffusing plate (2) was 0.5 × 10 ¹³ Ω / □.

  Next, using the light diffusing plate (2), the liquid crystal display device (1) having the structure shown in FIG. 2 was manufactured. A light diffusion film (thickness: about 150 μm) was used as the optical film (5), and a fluorescent tube was used as the light source (3). Moreover, in this liquid crystal display device (1), the diagonal length of the image display part in the liquid crystal panel (12) was designed to be 65 cm.

<Example 2, Comparative Examples 1 and 2>
Liquid crystal display in the same manner as in Example 1 except that the surface resistivity of both surfaces of the light diffusion plate (2) was set to the values shown in Table 1 by adjusting the content of the antistatic agent in the surface layer (22). A device was made.

<Example 3>
A liquid crystal display device was produced in the same manner as in Example 1 except that the diagonal length of the image display portion in the liquid crystal panel (12) was designed to be 80 cm.

<Example 4>
A liquid crystal display device was produced in the same manner as in Example 2 except that the diagonal length of the image display portion in the liquid crystal panel (12) was designed to be 80 cm.

<Comparative Example 3>
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the diagonal length of the image display portion in the liquid crystal panel (12) was designed to be 80 cm.

<Comparative Example 4>
A liquid crystal display device was produced in the same manner as in Comparative Example 2 except that the diagonal length of the image display portion in the liquid crystal panel (12) was designed to be 80 cm.

  Each liquid crystal display device obtained as described above was evaluated according to the following evaluation method. The results are shown in Table 1.

<Surface resistivity measurement method>
In accordance with JIS K6911, the surface resistivity (Ω / □) of the light diffusion plate was measured using an insulation meter (SM-8220, manufactured by Toa DKK Co., Ltd.) and a plate sample electrode (SME-811 manufactured by Toa DKK Co., Ltd.). ) Was measured. Before the measurement, the measurement sample was left for 6 hours under conditions of 23 ° C. × humidity 50% RH for condition adjustment.

<Evaluation of dust adhesion to the surface of the light diffusion plate>
After the liquid crystal display device was operated intermittently for one month (actual use time 10 days), the state of dust adhesion on the surface of the light diffusion plate was visually evaluated.

<Evaluation of screen unevenness>
The presence or absence of screen unevenness of the liquid crystal image after the liquid crystal display device was operated intermittently for one month (actual use time of 10 days) was visually evaluated.

  As is apparent from Table 1, in the liquid crystal display devices according to Examples 1 to 4 of the present invention, although the diagonal length of the image display portion in the liquid crystal panel is a large size of 60 cm or more, to the light diffusion plate surface It was possible to sufficiently prevent the dust from adhering to the screen and to prevent the occurrence of screen unevenness.

On the other hand, in the liquid crystal display devices of Comparative Examples 1 to 4, since the surface resistivity of the surface in contact with the air flow path in the light diffusion plate exceeds 1.0 × 10 ¹⁴ Ω / □, the surface of the light diffusion plate There was a lot of dust adhering to the screen, resulting in screen unevenness.

It is sectional drawing which shows one Embodiment of the liquid crystal display device based on this invention. It is sectional drawing which shows the liquid crystal display device which concerns on other embodiment. It is sectional drawing which shows the liquid crystal display device which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Light diffusing plate 3 ... Light source 4 ... Lamp box 6 ... Liquid crystal cell 7 ... Polarizing plate 8 ... Polarizing plate 10, 10X ... Air flow path 11 ... Surface light source device 12 ... Liquid crystal panel 21 ... Base layer 22 ... Surface

Claims (5)

A plurality of light sources are disposed on the back side of the light diffusion plate, a lamp box is disposed on the back side of the plurality of light sources, and a liquid crystal panel having a liquid crystal cell is disposed on the front side of the light diffusion plate. A display device,
The diagonal length of the image display part in the liquid crystal panel is 60 cm or more,
A surface of the light diffusing plate that is in contact with the air flow channel is provided with a vent channel that communicates with the outside for discharging heat generated from the light source to the outside of the apparatus. The surface resistivity of the liquid crystal display device is 1.0 × 10 ¹⁴ Ω / □ or less. 2. The air flow path is provided in contact with the light source side surface of the light diffusion plate, and the surface resistivity of the light diffusion side surface of the light diffusion plate is 1.0 × 10 ¹⁴ Ω / □ or less. The liquid crystal display device described. 2. The liquid crystal display device according to claim 1, wherein the ventilation channel is provided in contact with both surfaces of the light diffusion plate, and the surface resistivity of both surfaces of the light diffusion plate is 1.0 × 10 ¹⁴ Ω / □ or less.   The liquid crystal display device according to claim 1, wherein the light diffusion plate is made of a resin plate in which an antistatic agent is dispersed in a transparent resin.   The light diffusion plate is a laminate in which a surface layer in which an antistatic agent is dispersed in a transparent resin is laminated on a surface of the base layer in which a light diffusing agent is dispersed in a transparent resin, on the side in contact with the ventilation channel. The liquid crystal display device according to claim 1, comprising a plate.

Images